Rather than being a coincidence, or a campaign to tarnish Harmonix’s reputation as some have suggested, these reviews are legitimately from Harmonix employees, and the company confirmed as much:

Nordhaus’ review has a new paragraph attached to it saying that “it’s probably important that I note that I worked on the game and work for Harmonix. That being said, I’m confident that if I didn’t I would still give the game five stars” and that “music discovery, playing with your family and friends, and cooperation make Rock Band my favorite”. While many will appreciate the editing/removal of the reviews and the fact that Harmonix says that the reviews were not posted with “ill intentions,” had this not been caught by Redditors, it’s very likely that they would have stayed up as is and possibly duped shoppers into a purchase.

Some fans are also confused as to why the Harmonix employees thought that this was a good idea in the first place. Although the game’s launch has been a bit rocky (a lack of instrument bundles, and random song freezes being two prime examples), Harmonix had already pledged to fix those, and a blog post on the company’s websitee (which was posted before these reviews were published) states that a new Rock Band 4 patch will be out by the end of the month. So, it seems odd that Harmonix felt the need to do this but having been called out, it seems unlikely that the company will do this again.

Source: Destructoid, reddit